Otimização de géis de microemulsão como fluido de remediação a perda de circulação

Abstract

Lost circulation is a serious and costly problem for the oil industry and it may happen during a drilling in permeable formations, natural fractions or caves. To heal this lost, gel systems combined with Lost Control Materials (LCM) is used, this combination is called completion fluids. However, sometimes these fluids are not effective, and there is a need for new technologies to solve this problem. Approximately 85% of the gross weight of the coconut consists of the husks, which is accumulated in dumps or in the road margins, then its hernessing becomes necessary. This work aimed to develop a new generation of completion fluid using surfactant-based gels and coconut fibers in different granulometries, treated with microemulsions, to prevent losses in carbonates, water-wettable microfractures and to study the interactions between fiber-microemulsion, gel-rock, fiber-rock and analyze the capacity of remediate the lost and in situ gelling ability. For the tests with the surfactant-based gels, two anionic surfactants were tested one of them was soap base, used in the systems,1 (S1) and 2 (S2) and the other one was saponified castor oil - SCO, which generated the third system, S3. Two microemulsion systems were tested for the treatment of coconut fiber, one with cationic surfactant (CTAB) with three types of micelles (direct micelle (MD), bicontinuous (MB) and reverse (MR)), another with anionic surfactant (soap base) at the point of bi-continuous micelle (SB). These fibers was analyzed through the TG-DTA, SEM, XRD, FRX and contact angle analyzes. The completion fluids were characterized by rheology, weight and filtration. A lost circulation apparatus was developed and used with the formulation that presented the best performance, and an in situ gelling test was performed. The best completion fluid was S2 with fibbers mesh sizes # 35, # 100 and # 200 because presented a pseudoplastic behavior, with high viscosities (≈ 2000 cP) and tensions (≈ 70 Pa), characteristic of in situ gelling completion fluid, low filtrate volumes below 10 mL, and a rapid formation of filtercake (15 minutes). In the loss simulator apparatus, the S2 with granulometric fibers # 35, # 100 and # 200, treated with the SB, was able to reduce the permeability by 50% with the minimum mass (50 g) of the studied fluid. The fibers treated with the SB, presented affinity for the developed gel and allowed the gel spread on the surface of the pores of the rock, and presented the chemical affinity for the surface, facilitating the process of deposition and sealing the fractures. For this reason, fibers treated by SB were chosen as the LCM of the new product. In situ gelation test showed that at 70 ℃ the gelling happen in 40 seconds, excellent result, making operation quick, efficient and less costly, with less probe time support.